Metal Finishing Guide Book

2013

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goggles, face shield, boots, apron, and gloves should be worn by workers to minimize the potential for body contact with the acidic solutions. Acid cleaners containing fluoride compounds can result in severe tissue damage. Precautions should be taken to avoid any contact with fluoridecontaining solutions. If fluoride compounds are used, personnel should be trained in the treatment of fluoride burns. The use of acid cleaning compounds can result in the evolution of flammable and explosive hydrogen gas. Care should be taken to avoid uncontrolled release of pressure when parts are cleaned in sealed cleaning chambers. Sources of spark or flame that can ignite accumulated hydrogen should be identified and removed from the area in which acid cleaning is conducted. The use of acidic cleaners for cleaning sulfurized steel or parts that have sulfurized oil present can result in the generation of poisonous and flammable hydrogen sulfide gas. The same precautions employed for dealing with hydrogen evolution should also be employed for the potential evolution of hydrogen sulfide. Acid cleaner tanks and equipment should be properly vented to keep worker exposure to mists and vapors below OSHA limits. The reactivity of substrate material should be evaluated prior to acid cleaning to prevent violent reaction due to incompatibility and/or part damage. Alkaline Cleaners The use of alkaline cleaners containing strong alkaline compounds, such as sodium hydroxide and potassium hydroxide, can result in strong exothermic reactions when working solutions are made or replenished. Additions should be made to water or working solutions in a cautious, controlled fashion to prevent splashing and localized boiling. Additions should only be made to cool solutions (<100oF). Water should not be added to alkaline powders. The use of alkaline cleaners for etching or cleaning reactive metals, such as aluminum, zinc, or magnesium, will result in the evolution of flammable hydrogen gas that can accumulate in foam blankets or in enclosed cleaning equipment. Equipment should be ventilated and ignition sources should be removed from areas in which reactive metals are cleaned. The use of alkaline electrocleaners will result in the evolution of hydrogen and oxygen. Tanks should be well vented to remove these gases. Foam blankets on electrocleaners should be sufficient to prevent misting without excessive accumulation of hydrogen and oxygen. Disconnect current prior to removing work from electrocleaning tanks to prevent hydrogen explosions. Personnel using, handling, or working in areas where exposure to alkaline cleaners is possible must wear alkaline-resistant personal protection consisting of safety goggles, face shield, gloves, apron, and boots. Respiratory protection should be worn when dust or mist is a problem. Neutral Cleaners Although the destructive effect of neutral cleaners on body tissues may be minimal, in many cases these cleaners are used hot and the possibility of thermal burns from splashing may exist. Additions to working solutions should be made slowly and cautiously in a controlled manner to prevent splashing. Additions should only be made to cool solutions (<100oF). Equipment A preventive maintenance schedule should be implemented for the inspection and repair of defective cleaning equipment. Hoist systems, exhaust systems, 62

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